The objective of this study is to explain spatial variations in cardiovascular mortality by sex. Recognizing the interdependence of the various dimensions of the 'ecological complex', it is maintained that spatial variations in cardiovascular mortality by sex and the sex differentials in cardiovascular mortality are the consequences of environmental, sustenance organization, health technology, and demographic factors. The test of the model is based on U.S. county level cardiovascular mortality data for ages 25-65 for the period 1970-1980. The most distinctive feature of the results is that environment has the greatest impact on sex differentials in cardiovascular mortality followed by sustenance organization. In this regard, socioeconomic status is shown to be the single most important variable in explaining cardiovascular mortality rates for both sexes in most community types. The effect of health technology is not significant, and increased availability of health manpower and facilities are often found in conjunction with higher rates of cardiovascular mortality for both sexes. The results of this study confirm the importance of programs directed toward altering the basic environment and sustenance organization structures of communities rather than other ecological components such as health technology.